U.S. patent number 6,153,536 [Application Number 09/262,601] was granted by the patent office on 2000-11-28 for method for mounting wafer frame at back side grinding (bsg) tool.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Donald W. Brouillette, Ronald L. Mendelson.
United States Patent |
6,153,536 |
Brouillette , et
al. |
November 28, 2000 |
Method for mounting wafer frame at back side grinding (BSG)
tool
Abstract
A method for manufacturing a low profile semiconductor chip,
includes fabricating a semiconductor device on a semiconductor
wafer, grinding, with a grinding tool, a backside of the
semiconductor wafer to reduce a thickness thereof, and with the
wafer in the grinding tool, providing a support structure on the
ground backside of the wafer.
Inventors: |
Brouillette; Donald W.
(Georgia, VT), Mendelson; Ronald L. (Richmond, VT) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
22998226 |
Appl.
No.: |
09/262,601 |
Filed: |
March 4, 1999 |
Current U.S.
Class: |
438/758;
438/759 |
Current CPC
Class: |
B24B
1/00 (20130101); B24B 7/228 (20130101); B24B
41/06 (20130101); H01L 21/6836 (20130101); H01L
2221/68327 (20130101) |
Current International
Class: |
B24B
1/00 (20060101); B24B 41/06 (20060101); B24B
7/22 (20060101); B24B 7/20 (20060101); H01L
21/67 (20060101); H01L 21/68 (20060101); H01L
021/31 (); H01L 021/469 () |
Field of
Search: |
;257/700
;438/612,109,691,758,759 ;451/41 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
9193863 |
|
Jul 1997 |
|
JP |
|
63176265 |
|
Jul 1998 |
|
JP |
|
11145089 |
|
May 1999 |
|
JP |
|
Primary Examiner: Niebling; John F.
Assistant Examiner: Lindsay, Jr.; Walter L.
Attorney, Agent or Firm: McGinn & Gibb, P. C. Walter,
Esp; Howard J.
Claims
What is claimed is:
1. A method of manufacturing a semiconductor chip, comprising:
fabricating a semiconductor device on a semiconductor wafer;
grinding, with a grinding tool, a backside of the semiconductor
wafer to reduce a thickness thereof; and
with said wafer in the grinding tool, providing a support structure
on the ground backside of the wafer.
2. The method according to claim 1, wherein said wafer is mounted
to a taped frame before the wafer is removed from the grinding
tool, such that said wafer is removable from the grinding tool for
processing through subsequent process steps while mounted to the
support structure.
3. The method according to claim 1, further comprising providing an
additional support to support the wafer before removing the wafer
from the grinding tool for subsequent processing until dicing.
4. The method according to claim 3, wherein said additional support
comprises a substrate formed of at least one of rigid plastic and
metal.
5. The method according to claim 1, further comprising providing
one of a rigid and pliable material on the backside of the
wafer.
6. The method according to claim 5, wherein said rigid material
comprises a rigid plastic substrate with an adhesive layer
thereon.
7. The method according to claim 1, further comprising providing a
structural support on a front side of said wafer.
8. The method according to claim 1, wherein said structural support
on the front side of said wafer is mounted on said wafer prior to
said wafer entering the grind tool.
9. The method according to claim 1, further comprising holding a
frontside of said wafer with a vacuum chuck while said backside of
the wafer is ground.
10. The method according to claim 9, further comprising providing a
protective layer on said frontside of said wafer prior to said
wafer being held by said vacuum chuck.
11. A method of manufacturing a wafer, comprising:
fabricating a device on a wafer;
grinding, with a grinding tool, a side of the wafer to reduce a
thickness thereof; and
with said wafer in the grinding tool, providing a support structure
on the ground side of the wafer.
12. The method according to claim 11, wherein said wafer is mounted
to a taped frame before the wafer is removed from the grinding
tool, such that said wafer is removable from the grinding tool for
processing through subsequent process steps while mounted to the
support structure.
13. The method according to claim 11, further comprising providing
an additional support to support the wafer before removing the
wafer from the grinding tool for subsequent processing until
dicing.
14. The method according to claim 13, wherein said additional
support comprises a substrate formed of at least one of rigid
plastic and metal.
15. The method according to claim 12, further comprising providing
one of a rigid and pliable material on the backside of the
wafer.
16. The method according to claim 15, wherein said rigid material
comprises a rigid plastic substrate with an adhesive layer
thereon.
17. The method according to claim 15, wherein said rigid material
is above 0.5 mm to about 5 mm thick.
18. The method according to claim 12, wherein said structural
support on the front side of said wafer is mounted on said wafer
prior to said wafer entering the grind tool.
19. The method according to claim 12, further comprising holding a
frontside of said wafer with a vacuum chuck while said backside of
the wafer is ground.
20. The method according to claim 19, further comprising providing
a protective layer on said frontside of said wafer prior to said
wafer being held by said vacuum chuck.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a tool and method for
producing semiconductor chips, and more particularly to a wafer
frame mounting method for a backside grinding (BSG) tool.
2. Description of the Related Art
Conventional systems utilize semiconductor wafers that are usually
thinned by a backside grinding (BSG) process prior to being diced
into individual chips for packaging into modules. The final wafer
thickness depends on the package design and final module thickness
required for a given application. Generally, the conventional
grinding processes can produce an 8-inch diameter wafer to a
thickness of about 300 .mu.m without major difficulty.
However, thicknesses on the order of about 250 .mu.m or less are
difficult (if not impossible) to achieve by the conventional
grinding process because the wafer is too fragile to be handled
after the grinding operation. Thus, additional costly processing
steps, such as etching and/or polishing, are required to strengthen
the wafer, or the wafer is likely to be broken or damaged during
subsequent handling. This problem will be even more acute as the
wafer processing industry migrates to 12-inch wafers.
Additionally, wafers are often warped coming off of the grinder,
thereby making difficult the handling and placement of the wafers
into cassettes. It is envisioned that future higher density
products will have even higher levels of warpage after the grinding
operation.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems of the conventional
systems and methods, it is an object of the present invention to
provide a method for mounting the backside ground wafer to a
substrate prior to removing the wafer assembly (e.g., wafer and
substrate) from the backside grinding chuck.
In a first aspect, a method of manufacturing a low profile
semiconductor chip, according to the present invention, includes
fabricating a semiconductor device on a semiconductor wafer;
grinding, with a grinding tool, the backside of the semiconductor
wafer to reduce a thickness thereof; and while the wafer is in the
grinding tool, providing a support structure on the ground backside
of the wafer.
In a second aspect of the invention, an apparatus for manufacturing
such a chip is provided.
With the unique and unobvious structure and method of the
invention, the substrate will support the wafer until it is
segregated into dies and diced. The substrate can be a rigid or
pliable material which can be used as a substrate for dicing. Such
a method avoids additional costly processing such as etching and
achieves thickness of 250 .mu.m or less with minimal breakage and
damage to the wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages will be
better uderstood from the following detailed description of a
preferred embodiment of the invention with reference to the
drawings, in which:
FIG. 1 is a schematic diagram of a backside grinding process and a
tool therefor;
FIG. 2 is a flow diagram illustrating a preferred method of the
invention; and
FIGS. 3A-3C illustrate a cross-section of the layer configurations
after various processing steps, with FIG. 3A illustrating a layer
configuration after a rigid carrier is mounted to a wafer prior to
grinding, FIG. 3B illustrating a standard grind set-up, and FIG. 3C
illustrates the process after the tape frame mount has been
performed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Referring now to the drawings, and more particularly to FIGS. 1-3C,
a method and tool are shown according to a first embodiment of the
present invention.
Generally, in the invention, in a dicing process for the wafer,
devices are tested on the wafer, and the wafer is backside thinned.
Then, a support structure is provided on the ground surface while
the wafer is held at its front surface by a vacuum chuck that holds
the wafer during the grinding operation. Then the wafer is removed
from the chuck, a subsequent front-side protective film is removed,
the wafer is diced, and the support structure is either removed or
left in place. As a result, a suitable thickness of the wafer may
be achieved, without costly, additional processing, and without
breakage to the wafer.
In FIG. 1, an apparatus 100 is provided for processing a wafer 150
through various stages of loading 10, rough grinding 11, finish
grinding 12, a stage 13 of mounting the wafer to a substrate (e.g.,
rigid carrier 160 shown in FIG. 3A), and subsequent unloading 14
for further processing. The apparatus is, for example, a carousel
rotatable through such stages as shown in the direction of arrows
A.
The apparatus 100 may include a plurality of chuck members each
dedicated for use for a particular wafer. Thus, each chuck carries
a wafer through all of the processing stages. It is noted that
additional stages may also be provided as is known. For example,
there could be a third grinding stage and a washing/drying stage
before the wafer mounting to the substrate stage.
In FIG. 1, a taped frame (or substrate assembly) 20 is applied to
the wafer 150. It is noted that the wafer 150 has a frontside (not
illustrated) with a plurality of semiconductor devices being
provided thereon, and a backside 15. The frame is preferably a
taped frame having an adhesive (e.g., dicing tape 21) thereon. The
dicing tape provides a guide for subsequent dicing of the wafer
150.
The frame materials may be selectively chosen depending on the
application of the chips being formed, etc. Typically, the frame is
in the form of a ring and has a shape (e.g., diameter) slightly
greater (e.g., preferably a 1-inch clearance between the edge of
the wafer and the edge of the substrate assembly) than that of the
wafer 150 for protecting the wafer and allowing easy handling
thereof.
Once the wafer grinding is complete as shown at reference numeral
12, the wafer is typically washed and dried (not shown in FIG. 1).
Then, the wafer 13 is mounted to the taped frame 20 before the
wafer is removed from a grinding chuck 16. As shown, the wafer
backside 15 is facing upwardly, with the front side thereof laying
against on the grinding chuck (vacuum chuck) 16. After grinding,
the wafer in such a position is ready to receive the
frame/substrate assembly 20 having dicing tape/adhesive 21
thereon.
Briefly, the process of applying the wafer to the substrate
includes prefabricating a taped frame assembly, aligning the taped
frame to a wafer/chuck assembly, lowering the taped frame to
contact the backside of the wafer, and then using a
pressure-applying device (e.g., such as a roller and/or a
"squeegee") which applies pressure across film to laminate the
structure to the wafer.
Thereafter, the wafer can be removed from the grinding chuck 16
(e.g., the vacuum chuck) and processed through subsequent process
steps while mounted to the frame assembly 20. The frame assembly 20
provides support for the wafer 13 until final dicing and chip
placement.
If additional support is necessary, a rigid plastic or metal
substrate with an adhesive layer (e.g., or any structure/material
stronger than the thinned wafer; in the case of tape, it is not
stronger than the wafer but it isolates the wafer from
handling--frame is used) can be used to support the wafer before
removal from the grinding chuck 16 through subsequent processing
until dicing.
The materials should be light permeable if ultraviolet
(UV)-light-curable adhesives are used. As noted above, the material
and thickness of the frame/substrate assembly may be freely
selected based on the application involved.
Alternatively to mounting the backside grinding wafer to a
non-rigid or rigid substrate prior to removal from the grinding
chuck 16, the wafer could be mounted frontside to a rigid substrate
prior to the grinding operation. This operation would be especially
useful if there was a great deal of time or distance involved in
transporting the wafer assembly to the dicing stage. Preferred
materials for the rigid substrate may include adhesively mounted
plastic and/or metal substrates, and preferred thicknesses are
substantially within a range of about 0.5 to about 5.0 mm. The
rigid substrate may serve as a stabilizer for handling until the
wafer is mounted to a dicing frame. Adhesive tack may be provided
and is designed or adjusted by ultra violet curing to allow the
rigid substrate to be removed prior to dicing.
Turning to FIG. 2, a flowchart of the inventive method 200 for
processing the wafer is shown. In step 201, a plurality of
semiconductor devices (e.g., active semiconductor devices) are
formed on a front side of a wafer.
In step 202, the wafer backside is ground by a grinding tool.
In step 203, in the grinding tool used for grinding the backside of
the wafer, a support structure is provided on the ground backside
of the wafer. It is noted that backside cleaning and/or polishing
optionally could be performed between steps 202 and 203.
An etching or polishing step can be added to the grind tool after
the in-process mounting operation and removal of a frontside
protective tape, as shown in step 204. More specifically, a
protective tape 170 (170') is typically used to protect the front
side of the wafer during grinding (e.g. of the backside) from
damage incurred by virtue of the frontside's contact with, and
being held by, the vacuum chuck 16. It is noted that due to its
non-rigid or semi-rigid characteristic, the protective (adhesive)
tape 170 (170') is for preventing damage, not necessarily for
providing support to the thinned wafer. When the protective tape is
removed, some adhesive residue may remain on the frontside of the
wafer. Thus, the cleaning step would be desirable. The cleaning
step may include cleaning the wafer if necessary, by any of a
number of known methods.
Thereafter, the wafer is ready for dicing and is diced in step
205.
FIGS. 3A-3C illustrate a cross-section of the layer configurations
for various embodiments of the invention.
For example, FIG. 3A illustrates an alternate embodiment in which a
rigid carrier 160 (substrate) is mounted to the wafer prior to
grinding. Such a rigid substrate 160 provides stability to the
wafer prior to grinding. It is noted that the rigid carrier
optionally could have the adhesive tape 170 (e.g., a double-sided
adhesive tape) provided on a surface opposed to the wafer. Such a
double-sided adhesive layer 170 would protect the front side of the
wafer 150. However, the wafer could have the rigid carrier mounted
directly thereon with no intervening adhesive layer.
FIG. 3B illustrates a standard grind set-up in which the wafer 150
has no support member and is held by the vacuum chuck during
grinding. Further, a single-sided adhesive tape 170' could be
employed on the frontside of the wafer 150 to protect the same
during grinding.
Finally, FIG. 3C illustrates the wafer 150 being support after the
tape frame 20 has been mounted to the wafer after grinding by means
of adhesive or the like. The tape/frame mount 20 provides stability
to the thinned wafer after grinding. As before, the optional
frontside protective tape 170' is shown.
Thus, with the method of the invention, the substrate supports the
wafer until it is segregated into dies. The substrate can be a
rigid or pliable material which can be used as a substrate for
dicing. Such a method avoids additional costly processing such as
etching, and achieves a low profile wafer (i.e. with a thickness of
approximately 275 .mu.m or less) with minimal breakage and damage
to the wafer.
Further, the method inexpensively allows wafer thinning to minimal
dimensions and the invention allows minimal final package
thicknesses.
While the invention has been described in terms of preferred
embodiments, those skilled in the art will recognize that the
invention can be practiced with modification within the spirit and
scope of the appended claims.
* * * * *